C Native API

7/9/26About 9 min

C Native API

1. Overview

The C Native API (SessionC) is a C language wrapper for the C++ Session SDK. It is used in the same way as the C++ driver. You only need to include the additional header file SessionC.h. Compilation, linking, and runtime deployment share the same iotdb_session shared library as the C++ driver.

Thrift and Boost are already packaged into iotdb_session. Applications do not need to install Thrift or Boost headers/libraries separately.

Note: This feature is supported since V2.0.10.

2. Installation

2.1 Option 1: Use the precompiled SDK package (recommended)

CI publishes zip packages by platform/toolchain. The file name is in the form iotdb-session-cpp-<version>-<classifier>.zip. After extraction, the directory structure is as follows:

iotdb-session-cpp-<version>-<classifier>/
├── include/
│   ├── SessionC.h          # C Native API header file
│   ├── Session.h           # C++ API header file
│   └── ...
├── lib/
│   ├── libiotdb_session.so       # Linux
│   ├── libiotdb_session.dylib      # macOS
│   └── iotdb_session.dll + .lib    # Windows
├── cmake/iotdb-session-config.cmake
├── pkgconfig/iotdb-session.pc
└── examples/                       # Includes table_example.c

Select the classifier according to the target environment:

Target environment	classifier suffix
Linux x86_64, glibc >= 2.28	`linux-x86_64-glibc2.28`
Linux aarch64, glibc >= 2.28	`linux-aarch64-glibc2.28`
macOS x86_64	`macos-x86_64`
macOS arm64	`macos-aarch64`
Windows + Visual Studio 2017	`windows-x86_64-msvc14.1`
Windows + Visual Studio 2019	`windows-x86_64-msvc14.2`
Windows + Visual Studio 2022	`windows-x86_64-msvc14.3`
Windows + Visual Studio 2026	`windows-x86_64-msvc14.4`

Note: Do not use a higher-version client to connect to a lower-version server.

2.1.1 C program compilation example

Linux / macOS:

gcc -std=c11 table_example.c \
  -I"$IOTDB_SESSION_HOME/include" \
  -L"$IOTDB_SESSION_HOME/lib" \
  -liotdb_session -pthread \
  -Wl,-rpath,"$IOTDB_SESSION_HOME/lib" \
  -o table_example

Windows + MSVC:

Compile in the x64 Native Tools Command Prompt (or run vcvars64.bat first to initialize the environment):

set IOTDB_SESSION_HOME=C:\path\to\iotdb-session-cpp-<version>-<classifier>
cd /d %IOTDB_SESSION_HOME%\examples
cl /TC /std:c11 table_example.c /I "%IOTDB_SESSION_HOME%\include" ^
  /link /LIBPATH:"%IOTDB_SESSION_HOME%\lib" iotdb_session.lib
copy /Y "%IOTDB_SESSION_HOME%\lib\iotdb_session.dll" .

At runtime, place libiotdb_session.so / .dylib / .dll in the same directory as the executable, or configure the corresponding dynamic library search path for your platform.

2.1.2 Compile examples in the SDK package

Run the following commands in the root directory of the extracted SDK package. The examples/ directory must be at the same level as include/ and lib/.

cd iotdb-session-cpp-<version>-<classifier>
cmake -S examples -B examples-build -DCMAKE_BUILD_TYPE=Release
cmake --build examples-build

Windows + Visual Studio:

cd iotdb-session-cpp-<version>-<classifier>
cmake -S examples -B examples-build -G "Visual Studio 17 2022" -A x64
cmake --build examples-build --config Release

If the library is installed in another path, such as the source CMake installation directory iotdb-client/client-cpp/target/install, explicitly specify IOTDB_SDK_ROOT. This directory must contain include/ and lib/.

cmake -S iotdb-client/client-cpp/examples -B examples-build -DCMAKE_BUILD_TYPE=Release \
  -DIOTDB_SDK_ROOT=iotdb-client/client-cpp/target/install
cmake --build examples-build

Windows example:

cmake -S iotdb-client\client-cpp\examples -B examples-build -G "Visual Studio 17 2022" -A x64 ^
  -DIOTDB_SDK_ROOT=D:\iotdb\iotdb-client\client-cpp\target\install
cmake --build examples-build --config Release --target table_example

2.2 Option 2: Build from source

2.2.1 Install build dependencies (required only for source builds)

macOS

brew install bison boost openssl

Ubuntu 16.04+ or other Debian distributions

sudo apt-get update
sudo apt-get install gcc g++ bison flex libboost-all-dev libssl-dev cmake

CentOS 7.7+/Fedora/Rocky Linux or other Red Hat distributions

sudo yum update
sudo yum install gcc gcc-c++ boost-devel bison flex openssl-devel cmake

Windows

Install MS Visual Studio (2019+ recommended), and select the C/C++ IDE and compiler components with CMake support.
Install CMake.
Install Win_Flex_Bison, rename the executables to flex.exe and bison.exe, and add them to PATH.
Install Boost (optional, CMake can also fetch it automatically) and OpenSSL.
The CMake build compiles Thrift 0.23 from source. SSL is enabled by default. If system OpenSSL cannot be found, the build falls back to building OpenSSL from source.

2.2.2 Build

Clone the source code from git:

git clone https://github.com/apache/iotdb.git
cd iotdb

To use a specific release version, switch to the corresponding branch, such as 2.0.6:

git checkout rc/2.0.6

Run the Maven build in the IoTDB root directory (recommended):

# Linux / macOS: build and package the SDK
./mvnw -P with-cpp -pl iotdb-client/client-cpp -am -DskipTests package

# Windows (Visual Studio 2022 example)
.\mvnw.cmd -P with-cpp -pl iotdb-client/client-cpp -am -DskipTests package

If Boost is not added to PATH on Windows, append a parameter such as:

-Dboost.include.dir="C:\boost_1_88_0"

You can also use CMake directly:

cmake -S iotdb-client/client-cpp -B build
cmake --build build --target install

Linux release packages are built in the manylinux_2_28 container. The target machine requires glibc 2.28 or later. The current build no longer uses old parameters such as -Diotdb-tools-thrift.version=0.14.1.1-gcc4-SNAPSHOT.

Full verification with integration tests:

./mvnw clean verify -P with-cpp -pl iotdb-client/client-cpp -am

2.3 Build artifacts

After a successful build, C API related files are located as follows:

C API header file (source): iotdb-client/client-cpp/src/include/SessionC.h
C API header file (installation/SDK package): include/SessionC.h
Library files:
- Source build: iotdb-client/client-cpp/target/install/lib/
- Maven package: iotdb-client/client-cpp/target/iotdb-session-cpp-<version>-<classifier>.zip
- Linux: lib/libiotdb_session.so
- Windows: lib/iotdb_session.dll / lib/iotdb_session.lib
Example source code:
- Tree model: iotdb-client/client-cpp/examples/table_example.c
- Table model: iotdb-client/client-cpp/examples/table_example.c
Integration tests:
- Tree model: iotdb-client/client-cpp/test/cpp/sessionCIT.cpp
- Table model: iotdb-client/client-cpp/test/cpp/sessionCRelationalIT.cpp

3. Basic API description

Description: The C driver is used in the same way as the C++ driver. You only need to include the additional header file SessionC.h. Compilation, runtime behavior, and system dependencies are shared with the C++ driver.

3.1 Common conventions

3.1.1 Status codes and error messages

TsStatus: TS_OK (0) indicates success. Any non-zero value indicates failure.
Predefined error codes:
- TS_ERR_CONNECTION (-1)
- TS_ERR_EXECUTION (-2)
- TS_ERR_INVALID_PARAM (-3)
- TS_ERR_NULL_PTR (-4)
- TS_ERR_UNKNOWN (-99)
The implementation may also return other negative values, which must be interpreted together with ts_get_last_error().
The Session C++ API reports many errors through exceptions and does not return a unified status code. The C API uniformly returns the integer type TsStatus, and fine-grained error information can be obtained through ts_get_last_error().

const char* ts_get_last_error(void);

Returns the error message of the last failed C API call in the current thread. The returned pointer is valid until the next C API call in the same thread.

3.1.2 Memory and handle rules

All char* buf + int bufLen output parameters must be allocated by the caller.
CTableSession*, CTablet*, CSessionDataSet*, and CRowRecord* are opaque pointers. After successful creation, the caller must release them according to the conventions of each API.

3.2 Enumerations and constants

TSDataType_C (data type)

Enumeration value	Meaning
`TS_TYPE_BOOLEAN`	Boolean
`TS_TYPE_INT32`	32-bit integer
`TS_TYPE_INT64`	64-bit integer
`TS_TYPE_FLOAT`	Single-precision floating point
`TS_TYPE_DOUBLE`	Double-precision floating point
`TS_TYPE_TEXT`	Text
`TS_TYPE_TIMESTAMP`	Timestamp
`TS_TYPE_DATE`	Date
`TS_TYPE_BLOB`	Binary large object
`TS_TYPE_STRING`	String
`TS_TYPE_INVALID`	Invalid parameter/error path (not a server-side type)

TSEncoding_C (encoding)

TS_ENCODING_PLAIN, TS_ENCODING_DICTIONARY, TS_ENCODING_RLE, TS_ENCODING_DIFF, TS_ENCODING_TS_2DIFF, TS_ENCODING_BITMAP, TS_ENCODING_GORILLA_V1, TS_ENCODING_REGULAR, TS_ENCODING_GORILLA, TS_ENCODING_ZIGZAG, TS_ENCODING_FREQ

TSCompressionType_C (compression)

TS_COMPRESSION_UNCOMPRESSED, TS_COMPRESSION_SNAPPY, TS_COMPRESSION_GZIP, TS_COMPRESSION_LZO, TS_COMPRESSION_SDT, TS_COMPRESSION_PAA, TS_COMPRESSION_PLA, TS_COMPRESSION_LZ4, TS_COMPRESSION_ZSTD, TS_COMPRESSION_LZMA2

TSColumnCategory_C (table model column category)

Enumeration value	Meaning
`TS_COL_TAG`	TAG column
`TS_COL_FIELD`	FIELD column
`TS_COL_ATTRIBUTE`	ATTRIBUTE column

3.3 Handles, status codes, and constants

Name	C definition	Meaning	Lifecycle responsibility
`CTableSession*`	`typedef struct CTableSession_ CTableSession;`	Table model session	After `ts_table_session_new` / `ts_table_session_new_multi_node` succeeds, the caller calls `ts_table_session_close` if it has been opened, and then `ts_table_session_destroy`
`CTablet*`	`typedef struct CTablet_ CTablet;` (opaque)	Tablet batch writing, shared by tree and table models	After `ts_tablet_new` / `ts_tablet_new_with_category` succeeds, the caller calls `ts_tablet_destroy`
`CSessionDataSet*`	`typedef struct CSessionDataSet_ CSessionDataSet;` (opaque)	Query result set, shared by tree and table models	After a query API successfully returns `*dataSet`, the caller calls `ts_dataset_destroy`
`CRowRecord*`	`typedef struct CRowRecord_ CRowRecord;` (opaque)	Current row	When `ts_dataset_next` returns a non-null value, the caller calls `ts_row_record_destroy`
`TsStatus`	`typedef int64_t TsStatus;`	API execution result code	`TS_OK` is 0. Any non-zero value indicates failure
`ts_get_last_error`	`const char* ts_get_last_error(void);`	Error message of the last failed C API call in the current thread	The returned pointer is valid until the next C API call in the same thread

3.4 Common Tablet APIs

3.4.1 Creation and destruction

API signature	Function	Input parameters	Return value	Success condition	Failure condition	Resource responsibility
`CTablet* ts_tablet_new(const char* deviceId, int columnCount, const char* const* columnNames, const TSDataType_C* dataTypes, int maxRowNumber);`	Create a Tablet handle	deviceId: device or table name; columnNames / dataTypes: arrays of column names and types; maxRowNumber: maximum number of rows	`CTablet*`	Returns a non-null handle	Returns a null handle	Caller calls `ts_tablet_destroy`
`CTablet* ts_tablet_new_with_category(const char* deviceId, int columnCount, const char* const* columnNames, const TSDataType_C* dataTypes, const TSColumnCategory_C* columnCategories, int maxRowNumber);`	Create a Tablet with column categories (TAG/FIELD/ATTRIBUTE)	columnCategories: `TS_COL_TAG` / `TS_COL_FIELD` / `TS_COL_ATTRIBUTE`	`CTablet*`	Returns a non-null handle	Returns a null handle	Caller calls `ts_tablet_destroy`
`void ts_tablet_destroy(CTablet* tablet);`	Destroy a Tablet handle	tablet: handle to release	None	The handle must not be used after the call	-	Releases tablet

3.4.2 Data filling and state control

API signature	Function	Return value	Success condition	Remarks
`int ts_tablet_get_row_count(CTablet* tablet);`	Query the current valid row count of the Tablet	int	Row count >= 0	Read-only query
`TsStatus ts_tablet_set_row_count(CTablet* tablet, int rowCount);`	Set the valid row count of the Tablet	TsStatus	`TS_OK`	The valid row count must be set before writing
`TsStatus ts_tablet_add_timestamp(CTablet* tablet, int rowIndex, int64_t timestamp);`	Write a timestamp for the specified row	TsStatus	`TS_OK`
`TsStatus ts_tablet_add_value_bool(CTablet* tablet, int colIndex, int rowIndex, bool value);`	Write a Boolean value	TsStatus	`TS_OK`
`TsStatus ts_tablet_add_value_int32(CTablet* tablet, int colIndex, int rowIndex, int32_t value);`	Write an int32 value	TsStatus	`TS_OK`
`TsStatus ts_tablet_add_value_int64(CTablet* tablet, int colIndex, int rowIndex, int64_t value);`	Write an int64 value	TsStatus	`TS_OK`
`TsStatus ts_tablet_add_value_float(CTablet* tablet, int colIndex, int rowIndex, float value);`	Write a float value	TsStatus	`TS_OK`
`TsStatus ts_tablet_add_value_double(CTablet* tablet, int colIndex, int rowIndex, double value);`	Write a double value	TsStatus	`TS_OK`
`TsStatus ts_tablet_add_value_string(CTablet* tablet, int colIndex, int rowIndex, const char* value);`	Write a string	TsStatus	`TS_OK`	String memory is managed by the caller
`void ts_tablet_reset(CTablet* tablet);`	Reset the internal state of the Tablet for reuse	void	-	Does not release the object. Only clears the state

Description: The current SessionC implementation does not provide ts_tablet_add_value_object. Use the C++ Session API to write OBJECT values.

3.5 Common DataSet APIs

3.5.1 Iteration control and metadata

API signature	Function	Return value	Remarks
`void ts_dataset_set_fetch_size(CSessionDataSet* dataSet, int fetchSize);`	Set the fetch batch size of the result set	None
`bool ts_dataset_has_next(CSessionDataSet* dataSet);`	Determine whether there may be another row	bool	On failure, check `ts_get_last_error()`
`CRowRecord* ts_dataset_next(CSessionDataSet* dataSet);`	Get the next row record handle	Row handle pointer	Non-NULL indicates a valid row. NULL indicates end or failure
`int ts_dataset_get_column_count(CSessionDataSet* dataSet);`	Get the number of columns in the result set	int
`const char* ts_dataset_get_column_name(CSessionDataSet* dataSet, int index);`	Get a column name by index	String pointer	No buf/bufLen output
`const char* ts_dataset_get_column_type(CSessionDataSet* dataSet, int index);`	Get a column type name by index	Type name string pointer	No buf/bufLen output
`void ts_dataset_destroy(CSessionDataSet* dataSet);`	Release a query result set handle	None	After each non-null `CRowRecord*` returned by `ts_dataset_next`, call `ts_row_record_destroy` in time

3.5.2 Value access

API signature	Function	Return value	Remarks
`void ts_row_record_destroy(CRowRecord* record);`	Release a row record handle	None
`int64_t ts_row_record_get_timestamp(CRowRecord* record);`	Read the timestamp of the current row	int64_t	The timestamp is not read from DataSet
`int ts_row_record_get_field_count(CRowRecord* record);`	Read the number of fields in the current row	int
`bool ts_row_record_is_null(CRowRecord* record, int index);`	Determine whether the specified column is null	bool
`bool ts_row_record_get_bool(CRowRecord* record, int index);`	Read a Boolean value by column index	bool
`int32_t ts_row_record_get_int32(CRowRecord* record, int index);`	Read an int32 value by column index	int32_t
`int64_t ts_row_record_get_int64(CRowRecord* record, int index);`	Read an int64 value by column index	int64_t
`float ts_row_record_get_float(CRowRecord* record, int index);`	Read a float value by column index	float
`double ts_row_record_get_double(CRowRecord* record, int index);`	Read a double value by column index	double
`const char* ts_row_record_get_string(CRowRecord* record, int index);`	Read the byte view of a text/binary column	const char.	May contain `.`. Not a buf . bufLen pattern
`int32_t ts_row_record_get_date_int32(CRowRecord* record, int index);`	Read a DATE column and return an integer in YYYYMMDD format	int32_t	Returns 0 if the field is null, out of bounds, or not DATE
`size_t ts_row_record_get_string_byte_length(CRowRecord* record, int index);`	Read the byte length of a string/binary field	size_t	TEXT/BLOB/STRING, etc. Do not use strlen
`TSDataType_C ts_row_record_get_data_type(CRowRecord* record, int index);`	Read the data type enumeration by column index	Enumeration	Returns `TS_TYPE_INVALID` for invalid parameters or out-of-bounds indexes

3.6 Table model CTableSession API matrix

3.6.1 Lifecycle

API signature	Function	Return value	Resource responsibility
`CTableSession* ts_table_session_new(const char* host, int rpcPort, const char* username, const char* password, const char* database);`	Create a table model session	`CTableSession*`	If opened, call `ts_table_session_close` first, and then `ts_table_session_destroy`
`CTableSession* ts_table_session_new_multi_node(const char* const* nodeUrls, int urlCount, const char* username, const char* password, const char* database);`	Create a table model session (multi-node URL)	`CTableSession*`	Same as above
`TsStatus ts_table_session_open(CTableSession* session);`	Open a table model RPC connection	TsStatus	On failure, check `ts_get_last_error()`
`TsStatus ts_table_session_close(CTableSession* session);`	Close a table model connection	TsStatus	`ts_table_session_destroy` is still required
`void ts_table_session_destroy(CTableSession* session);`	Destroy a table model session handle	None	Releases session

Description: The database parameter is the default database name. Pass the empty string "" to leave it unset, and switch later through the USE SQL statement.

3.6.2 Writing and querying

API signature	Function	Return value	Resource responsibility
`TsStatus ts_table_session_insert(CTableSession* session, CTablet* tablet);`	Write data by Tablet in the table model	TsStatus	Ownership of tablet is not transferred
`TsStatus ts_table_session_execute_query(CTableSession* session, const char* sql, CSessionDataSet** dataSet);`	Execute query SQL in the table model	TsStatus	Caller calls `ts_dataset_destroy` for `*dataSet`
`TsStatus ts_table_session_execute_query_with_timeout(CTableSession* session, const char* sql, int64_t timeoutInMs, CSessionDataSet** dataSet);`	Execute a query with timeout in the table model	TsStatus	Same as above
`TsStatus ts_table_session_execute_non_query(CTableSession* session, const char* sql);`	Execute non-query SQL in the table model	TsStatus	No new handle

4. Sample code

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "SessionC.h"

#define HOST "127.0.0.1"
#define PORT 6667
#define USER "root"
#define PASS "root"

#define DB_NAME "cdemo_db"
#define TABLE_NAME "cdemo_t0"

static void fail(const char* ctx, CTableSession* s) {
  fprintf(stderr, "[table_example] %s failed: %s.", ctx, ts_get_last_error());
  if (s) {
    ts_table_session_close(s);
    ts_table_session_destroy(s);
  }
  exit(1);
}

int main(void) {
  /* The last parameter is the default database name. Pass "" to leave it unset and switch later through USE SQL. */
  CTableSession* session = ts_table_session_new(HOST, PORT, USER, PASS, "");
  if (!session) {
    fprintf(stderr, "[table_example] ts_table_session_new returned NULL: %s.",
            ts_get_last_error());
    return 1;
  }
  if (ts_table_session_open(session) != TS_OK) {
    fail("ts_table_session_open", session);
  }

  char sql[512];
  snprintf(sql, sizeof(sql), "DROP DATABASE IF EXISTS %s", DB_NAME);
  (void)ts_table_session_execute_non_query(session, sql);

  snprintf(sql, sizeof(sql), "CREATE DATABASE %s", DB_NAME);
  if (ts_table_session_execute_non_query(session, sql) != TS_OK) {
    fail("CREATE DATABASE", session);
  }

  snprintf(sql, sizeof(sql), "USE .%s.", DB_NAME);
  if (ts_table_session_execute_non_query(session, sql) != TS_OK) {
    fail("USE DATABASE", session);
  }

  const char* ddl = "CREATE TABLE " TABLE_NAME " ("
                    "tag1 string tag,"
                    "attr1 string attribute,"
                    "m1 double field)";
  if (ts_table_session_execute_non_query(session, ddl) != TS_OK) {
    fail("CREATE TABLE", session);
  }

  const char* columnNames[] = {"tag1", "attr1", "m1"};
  TSDataType_C dataTypes[] = {TS_TYPE_STRING, TS_TYPE_STRING, TS_TYPE_DOUBLE};
  TSColumnCategory_C colCategories[] = {TS_COL_TAG, TS_COL_ATTRIBUTE, TS_COL_FIELD};

  CTablet* tablet =
      ts_tablet_new_with_category(TABLE_NAME, 3, columnNames, dataTypes, colCategories, 100);
  if (!tablet) {
    fail("ts_tablet_new_with_category", session);
  }

  int i;
  for (i = 0; i < 5; i++) {
    if (ts_tablet_add_timestamp(tablet, i, (int64_t)i) != TS_OK) {
      ts_tablet_destroy(tablet);
      fail("ts_tablet_add_timestamp", session);
    }
    if (ts_tablet_add_value_string(tablet, 0, i, "device_A") != TS_OK) {
      ts_tablet_destroy(tablet);
      fail("ts_tablet_add_value_string tag", session);
    }
    if (ts_tablet_add_value_string(tablet, 1, i, "attr_val") != TS_OK) {
      ts_tablet_destroy(tablet);
      fail("ts_tablet_add_value_string attr", session);
    }
    if (ts_tablet_add_value_double(tablet, 2, i, (double)i * 1.5) != TS_OK) {
      ts_tablet_destroy(tablet);
      fail("ts_tablet_add_value_double", session);
    }
  }
  if (ts_tablet_set_row_count(tablet, 5) != TS_OK) {
    ts_tablet_destroy(tablet);
    fail("ts_tablet_set_row_count", session);
  }

  if (ts_table_session_insert(session, tablet) != TS_OK) {
    ts_tablet_destroy(tablet);
    fail("ts_table_session_insert", session);
  }
  ts_tablet_destroy(tablet);

  CSessionDataSet* dataSet = NULL;
  if (ts_table_session_execute_query(session, "SELECT * FROM " TABLE_NAME, &dataSet) != TS_OK) {
    fail("ts_table_session_execute_query", session);
  }
  if (!dataSet) {
    fprintf(stderr, "[table_example] dataSet is NULL.");
    ts_table_session_close(session);
    ts_table_session_destroy(session);
    return 1;
  }
  ts_dataset_set_fetch_size(dataSet, 1024);

  int count = 0;
  while (ts_dataset_has_next(dataSet)) {
    CRowRecord* record = ts_dataset_next(dataSet);
    if (!record) {
      break;
    }
    printf("[table_example] row %d: time=%lld.", count,
           (long long)ts_row_record_get_timestamp(record));
    ts_row_record_destroy(record);
    count++;
  }
  ts_dataset_destroy(dataSet);
  printf("[table_example] SELECT returned %d row(s)..", count);

  snprintf(sql, sizeof(sql), "DROP DATABASE IF EXISTS %s", DB_NAME);
  (void)ts_table_session_execute_non_query(session, sql);

  ts_table_session_close(session);
  ts_table_session_destroy(session);
  return 0;
}